oralce和db2兼容开发注意事项

数据库兼容，在开发项目过程中，难免会遇到 更改数据库，或者后期 项目升级，也可能会遇到这种情况，这里就说明下oralce和db2兼容开发注意事项。

兼容oralce、db2开发注意事项

（前提是db2版本是9.7，且是开启PLsql编译选项之后创建的数据库)：

1. 在like 之后若使用了表字段，应统一改成使用locate函数

如：
oralce写法：
select * from fw_right a where '03' like a.rightid||'%';
兼容写法：
select * from fw_right a where locate('03',a.rightid) = 1;
oralce写法：
select * from fw_right a where '03' like '%'||a.rightid||'%';
兼容写法：
select * from fw_right a where locate('03',a.rightid) > 0;

2. 视图中使用的别名不应该与当前表字段同名

如以下语句，在Oracle中不会有问题，但在db2中会报"sql0153N"错误：

rush:sql;"> e.g: CREATE OR REPLACE VIEW V_WF_TodoLIST AS select c.process_def_id,c.process_def_name,a.action_def_id,a.work_item_id,a.bae007,a.action_def_name,a.state,a.pre_wi_id,a.work_type,a.operid,a.x_oprator_ids,b.process_key_info,to_char(to_date(a.start_time,'yyyymmddhh24miss'),'yyyy-mm-dd hh24:mi:ss') as start_time,to_char(to_date(a.complete_time,'yyyy-mm-dd hh24:mi:ss') as complete_time,a.filter_opr,a.memo,a.bae002,a.bae003,a.bae006,c.x_action_def_ids from wf_work_item a,wf_process_instance b,wf_action_def c where a.action_def_id = c.action_def_id and b.process_def_id = c.process_def_id and a.bae007 = b.bae007 and a.state in('0','2')

兼容写法：

rush:sql;"> CREATE OR REPLACE VIEW V_WF_TodoLIST AS select c.process_def_id,'yyyy-mm-dd hh24:mi:ss') as start_time_0,'yyyy-mm-dd hh24:mi:ss') as complete_time_0,c.x_action_def_ids from wf_work_item a,wf_action_def c where a.action_def_id = c.action_def_id and b.process_def_id = c.process_def_id and a.bae007 = b.bae007 and a.state in('0','2')

3.在下列情况下不允许 ORDER BY 或 FETCH FirsT n ROWS ONLY：

* 外层全查询视图
* "sql 表函数"的 RETURN 语句中的外层全查询
* 具体化查询表定义
* 未用圆括号括起来的子查询

否则会报"sql20211N 规范 ORDER BY 或 FETCH FirsT n ROWS ONLY 无效。"错误.

e.g:
oralce写法：

rush:sql;"> CREATE OR REPLACE VIEW V_FW_BLANK_BULLETIN as select id,bae001,operunitid,operunittype,unitsubtype,ifergency,title,content,digest,duetime,validto,aae100,bae006,bae002,bae003,id as colid,substr(digest,1,20) as digest2 from fw_bulletin where duetime <= to_char(sysdate,'yyyymmddhh24miss') and (to_char(validto) >= to_char(sysdate,'yyyymmddhh24miss') or validto is null) and aae100 ='1' order by ifergency desc,id desc,duetime desc

兼容写法：

rush:sql;"> CREATE OR REPLACE VIEW V_FW_BLANK_BULLETIN as select * from (select id,20) as digest2 from fw_bulletin where duetime <= to_char(sysdate,'yyyymmddhh24miss') and (to_char(validto) >= to_char(sysdate,'yyyymmddhh24miss') or validto is null) and aae100 ='1' order by ifergency desc,duetime desc)

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